(1) Field of the Invention
The present invention relates to an electrically conductive composition for electro-responsive recording materials. More particularly, the invention relates to an electrically conductive composition for electro-responsive recording materials, which has in combination highly improved electric conductivity, low humidity dependency, reduced tacking tendency and high whiteness and which can be manufactured at a low cost.
By the term "electro-responsive recording material" is meant a recording material capable of performing recording in response to electric signals or performing recording by utilizing an electric energy and other energy, for example, light energy, in combination. As the recording material included in the concept of the electro-responsive recording material, there can be mentioned, for example, an electrolytic recording material, an electric discharge recording material, an electrostatic recording material and an electrophotographic photosensitive recording material. Irrespective of the image forming mechanism, in order to form a clear image promptly, it is important that each of these electro-responsive recording materials should satisfy the requirement that an appropriate electrically conductive layer should be present in the material when it is actually applied to the recording operation.
(2) Description of the Prior Art
As the conducting agent for rendering these recording materials electrically conductive, there are known various substances, for example, metal powders, carbon black, water-soluble and moisture-absorptive inorganic and organic salts, surface active agents, wetting agents such as polyhydric alcohols, and polymeric electrolytes, and these conducting agents are actually used in the art. These known conducting agents, however, have some defects or other and are still insufficient in various points.
For example, conducting agents such as metal powders and carbon black are good conductors and they have a merit that their electric conductivity is not influenced by the humidity, but they have a fatal defect that they generally have an inherent color or opacity. From the viewpoints of the sharpness and contrast of formed images, it is important that a recording material should be excellent in the whiteness, and it is generally desired that recording materials having images formed thereon may be used as originals for customary copying processes such as diazo and electrophotographic copying processes. Recording materials including a metal powder or carbon black as the conducting agent fail to meet this requirement. Moreover, the weights of recording materials of this type are heavy and they are relatively expensive.
Other conducting agents such as salts, activating agents, organic wetting agents and polymeric electrolytes are rendered electrically conductive only in the presence of water, and therefore, they inevitably involve various defects. For example, electrolytic recording materials comprising a salt or the like as the conducting agent must be used in the humidified state (wet state), and especial care should be taken to storage conditions prior to actual application. Moreover, in case of these recording materials, since recording is carried out according to a wet method, bleeding is readily caused in a formed image. Further, an electrostatic recording material or electrophotographic recording material comprising an electrically conductive layer composed of a polymeric electrolyte such as a cationic conductive resin or anionic conductive resin has a merit that it need not be used in the especially humidified state, but its electric conductivity is greatly influenced by the humidity. For example, when a recording material of this type is allowed to stand in a low humidity atmosphere for a long time, the image sharpness is drastically degraded by reduction of the electric conductivity. On the other hand, in a high humidity atmosphere, because of the water solubility of the polymer electrolyte, there is brought about a disadvantage that recording sheets readily tack each other.